Most systems for generating electrical power currently in use employ steam turbines as the motive means for operating the generators. The heat necessary for generating steam in sufficient quantities to operate a conventional electrical power generating plant is enormous and the sources from which such heat is derived are both expensive and cause certain ancillary problems. The most commonly used heat source materials currently being used are both expensive and are nonrenewable natural resources. Additionally, the burning of such fuels causes environmental problems unless substantial emission controls are employed, which controls are exceedingly expensive and reduce the efficiency of the system.
There are also in current use nuclear fuels which are used as heat source materials for generating steam for electrical power generation. However, the cost of nuclear fuel is high and the operation of this type of plant is expensive and difficult. While the supply of such nuclear fuels is virtually unlimited, safety measures are exceedingly difficult and expensive as is the initial construction of such nuclear power plants.
There have been considerable efforts expended in searching for alternate sources of energy to generate electrical power. Such alternate sources of energy have included wind energy, tidal energy and geothermal energy. Windmills for generating electrical power are in use, but are extremely limited in capacity and, to date, are very expensive. Tidal power plants are also in use, but require very special conditions which have limited their application to only a very few areas on the earth.
For geothermal power plants, it has heretofore been the practice to locate such plants only in the vicinity of faults in the earth's crust where the extremely high temperatures of the earth's core are relatively readily available. Such faults exist, however, only in a very few places and therefore geothermal power plants have not been extensively used.
With all of the steam-electrical generating systems currently in use, the condensation of the steam and the disposal of the heat absorbed by the coolant also poses substantial problems. The volume of cooling water required to effect such condensation is considerable and therefore such plants must be located adjacent a relatively large supply of water. In some of the more arid areas, this is a problem of considerable magnitude. Further, the effluent water is at a higher temperature and this poses certain environmental problems. The use of "cooling towers" poses high initial costs and high operating costs. To my knowledge, all such systems dispose of the heat absorbed by the cooling water and no attempts have been made to recoup any of this heat.
It is common knowledge that the center of the earth is extremely hot and that a skin of very dense rock separates the hot interior from the surface of the earth. Although this rock in the earth's skin is resistant to the passage of heat, nevertheless a small amount of heat per unit area is transmitted from the hot interior of the earth to the surface of the earth. The amount of heat transmitted from the center of the earth to the surface is found to be--
Heat (calories)=1.2.times.10.sup.-6 per square cm. per second or 15.9 BTUs per square foot per hour.
The heat so transmitted through the earth's skin is absorbed by subterranean water which flows through a system of veins. These veins practically blanket the surface of the earth adjacent to the rock skin and vary in depth from the surface of the earth from approximately 100 feet to several hundred feet. In the Piedmont section of North Carolina and South Carolina, the depth is usually from 100 to 200 feet and the temperature of the water is substantially constant at approximately 60 degrees F. The temperature of the subterranean water in all areas of the United States is shown on page 155 of the September, 1980 issue of Popular Mechanics magazine. This temperature of the subterranean water is maintained by a loss of heat by conduction to the surface of the earth. The earth, stone, etc. between the subterranean water and the surface of the earth are fairly good conductors of heat because of the presence of moisture in the soil. Therefore, the input of heat from the center of the earth is balanced by the loss of heat, over a considerable time, from the subterranean water through the surface of the earth.
While it has been previously suggested that certain systems which employ coils, tanks or other liquid containers buried in the earth at depths ranging from open containers to coils or closed tanks buried several feet beneath the surface of the earth, be used as heat sources for heating enclosed spaces, these heat sinks have been limited in application even for residential heating purposes.